Normal embryology of the respiratory system Sept28 M3 Flashcards
embryonic origin of resp lining epithelium (trachea, bronchi, alveoli)
embryonic endoderm
embryo origin of pleural cavity
embryonic mesoderm
when pleural cavity formed
very early in embryogenesis (flat trilaminar embryo phase) in the intra embryonic mesenchyme
how trilaminar embryo fols 3 body cavities
forms horseshoe-shaped cavity that divides into pericardial cavity, pleural (thorax) and peritoneal (abdominal-pelvic region)
cavities formed after the horseshoe-shaped cavity separates
pericardial, left and right pleural cavity, left and right peritoneal cavity
because the cavities are formed from mesenchyme, we’ll say that a ___________ is formed
mesothelium
what lines cavities and why
coelomic epithelium because the cavity forms in the mesenchyme
4 week embryo: result
cylindrical embryo envelopped in fluid filled amniotic sac
primitive organ systems are enveloped in the 3 definitive body cavities by intra-embryonic coelom
how primitive gut forms
- have amniotic cavity that expands in extra-embryonic cavity
- yolk sac protrudes in space between yolk sac and amniotic cavity to form foregut, midgut, hindgut
embryonic origin of the primitive gut and why
endoderm (bc are expansion of yolk sac)
origin of the respiratory system and important thing to form it
foregut. Amniotic fluid plays an important role
organs that the foregut produces
pharynx, esophagus, resp system, stomach, proximal duodenum, liver, pancreas
why diaphragm formation is important
provides comparmentalization, to make space for lungs and separate thorax from abdomen
what provides gaseous exchange prenatally
placenta
structures of the primitive gut
buccopharyngeal membrane, foregut, midgut, hindgut, cloacal membrane
how the gut is canalized
apoptosis from buccopharyngeal membrane (week 4) to cloacal membrane (week 7)
where undetached pleural cavity is present near the primitive gut
on sides of the foregut
what is the septum transversum
mesenchyme on which the heart and pericardial cavity lies and that is continuous with the forming membrane that will separate the pleura and peritoneal cavity
what diaphragm comes from and why
from septum transversum, it is the membrane that separates pleural and peritoneal cavity.
origin of septum transversum
mesenchyme that came from cervical region and migrated to reach its position. Took with it nerves from cervical spinal cord
consequence of herniation through the diaphragm
hypoplasia of the lungs bc abdominal organs herniate into thoracic cavity
common sites of herniation through diaphragm
- through pleuro-peritoneal membrane on left of the mediastinum (Foramen of Bochdalek)
- anteriorly and parasternally (Formane of Morgagni x2)
important factor determining if embryonic herniation will be viable
time of closure of foramens of Bochdalek and Morgagni.
- Early herniation: severe hypoplasia-death.
- Midler defect-weakness could simply appear later in life
Respiratory system origin
endoderm and foregut
After cavities seaprate and diaphragm present, how lungs develop and what diaphragm does
will start branching. diaphragm starts to contract
initial structure where trachea and bronchi will come from
foregut, primitive pharynx: splanchnopleure (mesenchyme) surrounds foregut in which endodermal apoptosis is occuring
first step to trachea and bronchi formation
laryngo-tracheal groove forms and its bottom is a tracheo-esophageal septum
2nd step to trachea and bronchi formation
laryngo-tracheal groove creates lung buds (branches) at the bottom
what allows pinching off of the trachea
trachea-esophageal mesenchyme. interacts with the endoderm and it’s genetically controlled
